In-ding repair tool

ABSTRACT

A repair tool for repairing an indented surface area of a sheet metal panel, such as a vehicle body panel, the repair tool including a stud welding gun with an air actuated piston and cylinder mechanism coupled to the welding gun electrode and to a stud latch mechanism whereby a stud can first be welded to the indented metal and then gripped by the latch mechanism after which actuation of the piston and the cylinder mechanism will provide the necessary force for raising the depressed metal to the normal plane of the surrounding sheet metal of the panel.

United States Patent [191 [1 3,801,772 Curcio et al. Apr. 2, 1974 [5IN-DING REPAIR TOOL 2,945,118 7/1960 Kelemen et al 219/98 [75]Inventors: Joseph Curcio, Southfield; Perry P.

Hufstetler, Mt. Clemens; Roger W. Primary Examiner j'v Truhe Johnson,Rochester, all of Mich- Assistant ExaminerClifford C. Shaw Attorney,Agent, or Firm-Arthur N. Krein [7 3] Assrgnee: General MotorsCorporation,

D t o't, M' h.

e r I 57 ABSTRACT 22 F'] d: A 7 l 73 l l l e ug A repair tool forrepairing an indented surface area of [21] Appl. No.: 392,070 a sheetmetal panel, such as a vehicle body panel, the

repair tool including a stud welding gun with an air ac- [52] U S Cl219/98 29/401 tuated piston and cylinder mechanism coupled to the [51]B23k 9/20 welding gun electrode and to a stud latch mechanism I wherebya stud can first be welded to the indented [58] Field of Search 219/98,99, 107, 29/401 metal and the" g pp y the latch mechanism after [56]References Cmd which actuation of the piston and the cylinder mechanismwill provide the necessary force for raising the UNITED STATES PATENTSdepressed metal to the normal plane of the surround- Sanchez sheet metalof the paneL 2,946,l l8 7/1960 Steck 29/401 3,321,607 5/1967 Falcone etal. 219/98 6 Claims, 5 Drawing Figures f 14 4 a: /xa 22 m1 1 2! g zx/ 2a7 i, age lat-iv, 5m; 7, b l 4 t. Ma g t "'"fi i a i; u i w l. I 671 [Mlg flllfllfllvlllltwlsm w 7 :7 :7 0 ,7

w a? 56' t ,o II at {a 2+ 2|; EXHAUST 1 IN-DING REPAIR TOOIL Thisinvention relates to apparatus for repairing damaged sheet metal and, inparticular, to an in-ding repair tool.

Sheet metal panels, such as vehicle body panels, are often damaged, asby hail stones or other objects, in a manner to cause areas of the sheetmetal to be deeply depressed relative to the normal plane of the sheetmetal panel. Such a deep depression or indentation of the metal in thismanner is commonly referred to as an in-ding with the damaged areaappearing as a concave surface area extending beneath the normal planeof the panel. This damaged area, in order to be properly repaired, mustbe brought back into the normal plane of the sheet metal. When thisdamage is accessible from the underside of the panel, it can readily beraised, for example, by the use of a pick hammer. However, when thisdamage is not readily accessible from the underside of the panel, thedamaged area can be repaired by welding a stud in the center of thedepression and then raising this portion of the panel by means of thestud.

In one method of arc welding the end of a metallic stud to a sheet metalpanel, a stud is employed having a small projection at its end to bewelded. The stud is positioned for welding with the projection locatedin contact with the workpiece and is biased toward the workpiece byadetermined force. Welding of the stud is accomplished by passingcurrent through the stud and workpiece, preferably by the discharge of acapacitor. The current causes the projection, which is relatively small,to disengage almost instantly, allowing the stud to move toward thepanel, and produces an arc between the end of the stud and the panelduring movement of the former into contact with the latter.

The apparatus for performing this method of welding generally comprisesa hand-operated welding gun and an electrical control power'pack forsupplying welding current to the welding gun. The welding gun functionsto hold the stud, position the stud relative to the workpiece and incontact therewith, bias the stud toward the workpiece witha'predetermined force, trigger the discharge of a capacitor and conductthe current therefrom through the stud and workpiece.

After the stud has been welded into the center of the depression of thepanel, a slide hammer is connected to the stud to effect raising of thedepressed metal back up into the plane of the sheet panel membersurrounding the previously damaged area. After this is done, the head orcollar of the stud is cut off and then the remainder of the stud isremoved by grinding or filing to obtain a smooth surface area, oralternately, the entire stud can be removed by grinding or filing.

In the method of removing an in-ding as just described using a studwelded into the concave depression or in-ding, it is necessary to firstuse a welding gun to weld the stud in place after which the operatorwould be required to remove the welding gun and then pick up a slidehammer placing the craw thereof over the head of the stud and theneffecting operation of the slide hammer to raise the concave surfacedin-ding up to or slightly above its normal surface plane, this latteroperation requiring operator skill.

It is therefore an object of the present invention to provide an in-dingrepair tool whereby a stud can be installed in the center of an in-dingor concave depression and then gripped and pulled on to raise thedepressed metal back to its normal surface plane.

Another object of this invention is to provide an inding repair too]including a weld gun in which the electrode thereof is connected to afluid actuated piston to effect raising of a depressed metal surfacearea after a stud has been welded thereto by actuation of the weldinggun.

These and other objects of the invention are attained by means of anin-ding repair tool for securing a stud to a depression in a sheet metalpanel and then raising the depression, the repair tool including awelding gun having a piston retaining shaft and a stud holder probeelectrode extending therefrom, a piston being fixed to the shaft with afluid cylinder reciprocably encircling the piston with one end of thefluid cylinder positioned to abut against the sheet metal panel, thetool having an electrical switch to control a stud welding operation anda valve acutator switchto control operation of the fluid cylinder andpiston mechanism of this repair tool.

For a better understanding of the invention as well as other objects andfurther features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a view, partly in section, of an in-ding repair tool inaccordance with the subject invention;

FIG. 2 is an end view taken along line 2 2 of FIG.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1 illustratingthe pivotal arrangement of the stud latch mechanism;

FIG. 4 is an enlarged perspective view of a portion of the stud holderprobe electrode of the tool; and,

FIG. 5 is a schematic electrical wiring diagram of the actuator switcheson the stud welding gun portion of the repair tool of FIG 1.

Referring now to the drawings, the subject in-ding repair tool, ahand-held tool generally identified by reference numeral 10, includes acommercially available stud welding gun 11 connected by a weldingcurrent cable 12 and a control cable 14 to a suitable commerciallyavailable electrical control power pack, not shown, which would alsoinclude a ground cable, not shown, for attachment to the vehicle bodypanel 15, on which a weld stud 16 is to be fastened to effect repair ina manner to be described of a depression or concave in-ding 15a in thepanel.

The stud welding gun 11 shown is a KSM Bantam C gun available from KSMWelding Systems Division of Omark Industries, Morristown, New Jersey,but modifled as hereinafter described.

As shown, the stud welding gun 11 includes a gun housing 17 having abarrel portion and a pistol grip portion 17b, the barrel portion havinga longitudinal bore therethrough including an enlarged bore portion 18aat the rear end or right-hand end of the barrel as seen in FIG. 1, anenlarged bore portion 18b at the front end thereof and an intermediatebore portion of reduced diameter therebetween, 'an intervening shoulder20 being provided between the bores 18a and 180 and an interveningshoulder 21 between bores 18b and 18c.

A spacer bushing 22 having a bore 22a therethrough to the rear end ofthe barrel portion 17a of the gun 22, rear cover 23 and front cover 24are formed of an electrically non-conducting material,.such as asuitable plastic material for this purpose.

Slidably mounted within the barrelportion 17a of the gun housing istheshaft 25 portion of an electrode spindle assembly 26, the rear portionor right-hand end of the shaft 25, as seen in FIG. 1, being slidablyjournalled in the bore 22a of spacer bushing 22, the electrode spindleassembly 26 being further slidably journalled in a shoulder bushing 27,of nylon for example, extending through the aperture 24a in front cover24.

. Shaft 25 and therefore electrode spindle assembly 26 is normallybiased in one direction, in a direction toward the front of the barrelof the gun housing by means of a spring 28 encirclingshaft 25 in bore18b, one end of this spring abutting against a spring retainer washer 30positioned against shoulder 21 and the other end of the spring abuttingagainst a radial flange 25a extending outward from the front end ofshaft 25.

Shaft 25 has one end of the welding current cable 12 suitably fixedthereto and'this shaft as a part ofa conventional electrode spindleassembly would normally have fixed directly thereto a stud holder toretain a weld stud, such as stud 16, to be welded onto a sheet metalpanel, the welding gun operator effecting the initiation of the weldcycle by actuation of the trigger button 31 ofa normally open switchSW-l not shown, except schematically in the wiring diagram of FIG. 5,mounted inside the pistol grip portion 17b of the gun, this switch beingsuitably connected to the conductor wires of control cable 14.

A more detailed description of the stud welding gun 1 l is' not deemednecessary for an understanding of the invention in the subject repairtool, since as previously described, the stud welding gun is aconventional, com- -mercially available stud welding gun, as thus fardescribed.

However, for a more detailed description of a typical,conventional'p'rior art type stud welding apparatus including the studwelding gun and the electrical circuit of the electrical control powerpack for it, reference is made to US. Pat. No. 2,945,l 18, issued July12, 1960, to Frank K. Keleman and Ralph K. Ritter.

Now, in accordance with a preferred embodiment of the invention,the-shaft 25 is provided at one end, the rear or right-hand end as seenin FIG. 1, with an internal threaded bore to adjustably receive thethreaded end 32a of a tapered switch acutator rod 32 having anoval-shaped free end 32b, the actuator rod 32 extending axially outwardfrom and concentric with the axis of the shaft 25 in position to actuatethe movable contact of a normally open switch SW-2 fixed to a notchedrear end portion of the spacer bushing 22, switch SW-2 being connectedin series with switch SW-l to the conductor wires of control cable 14,as seen in FIG. 5. I

Now, in accordance with the invention, the electrode spindle assembly 26of the subject repair tool includes a piston shaft 40, fixed at one endto shaft 25, as by threaded stud 41 engaged in both of these elementsand, at its otherend is secured to a stud holder probe electrode 42adapted to hold the weld stud 16. The end of piston shaft 40, fixed toshaft 25, is slidably jourwhich terminates at a radial inward extendingwall 46 having a bore 46a therethrough. Cylinder 43 further includes apair of spaced apart web legs 47 extending axially outward from wall 46,opposite cylinder portion 44, to support an oval-shaped seat or footportion 48,

as best seen in FIG. 2, which is provided with a suitable groove on theother free face surface thereof to receive an O-ring 50 which is securedtherein, as by means of a suitable adhesive.

The piston shaft 40 is mounted for reciprocable 'movement relative tothe cylinder 43 by being suitably journalled in a shoulder bushing 51extending through the apertured end cap 52 fixed tothe free end of thecylindrical portion 44 of the cylinder 43 to partly close off the openend thereof and, in a shoulderedbu'shing 53 positioned in the bore 46aof wall 46, these bushings also being made of a suitable material, suchas nylon. The piston shaft 40 carries a piston 54 fixed thereto as by apin 55 for reciprocating movement in the bore 45 of the cylinder portion44 of cylinder 43.

. Movement of the cylinder 43 relative to the piston 54, in onedirection, a direction toward stud welding gun 11, is effected by meansof a coil spring 56' encircling shaft 40 with one end of the springabutting end cap bushing 51 and the other end abutting against thepiston 54, with movement of these elements relative to each other in theopposite direction being affected by the introduction of a fluid under.pressure through an inlet port 57 in the wall46, this inlet portextending into the variable volume cavity in the cylinder portion 44formed between-the wall 46 and the piston 54 in bore 45. Movement ofthese elements in this last described direction is limited by means of acylindrical stop 58 encircling the shaft 40 and spring 56 with one endof this stop in'abutment against the end cap bushing 51 and the otherend in position to be engaged by the piston 54. 1

Inlet port 57 is connected; by flexible conduit 60 to a conventionalpush button 61 actuated fluid control valve 62 fixed to the pistol gripportion 17b of the stud welding gun whereby conduit 60, which isnormally in communication through the valve 62 with an exhaust port 63open to the atmosphere can, upon actuation of the push button 61, beplaced in fluid flow communication with a conduit 64 secured at one endto the inlet of this valve 62 and is adapted at its other end to beconnected by a quick connect coupling 65 to a source, not shown, offluid under pressure such as pressurized air.

Although any suitable stud holder probe electrode having a suitablemeans to hold a stud 16 to effect welding of it to a panel can be used,as well as any suitable means to then grip the head of the stud afterwelding to effect raising of the depressed metal of the damaged panel,in the preferred embodiment, the probe electrode is provided with acollet chuck at its free end and, a pivotal latched mechanism isassociated with the probe electrode to retain the stud in the colletchuck of the probe electrode during actuation of the fluid cylinder andpiston mechanism to raise the depressed metal portion of the panel.

Thus, in the preferred embodiment illustrated, the stud holder probeelectrode 42 is provided with a threaded stub 70 at one end thereofsecured in the threaded aperture, provided for this purpose, in the endof piston shaft 40, an intermediate shaft 71 portion extending from thestub shaft 70, to in effect form an extension of the piston shaft 40,and a terminal reduced diameter spindle 72 portion extending axiallyoutward from shaft 71.

Spindle 72 is provided with an axial stepped bore extending from thefree end thereof and with a plurality of slots 73 extending through thewall of this portion of the spindle to the stepped bore to provide aplurality of somewhat flexible segments 72a forming a collet chuck atthe free end of the spindle, the collet chuck thus formed having avariable inner diameter surface 74 of a desired size to accommodate thehead of a stud 16, the head of which would s'eat against shouldersegments 75 within the enlarged bore portion of spindle 72.

The shaft 7l'portion of the probe electrode 42 is provided with opposedflat sides 71a on a portion thereof, with a through bore extending fromone of these sides to the other side, this bore being adapted to receiveat opposite ends thereof the shouldered bushings 76, whereby a latch 77can be pivotably supported on the probe electrode 42 by means of a pin78 journalled in the bushings, the pin 78 being axially retained in thebushings by means of split ring retainers 80 positioned in suitablegrooves provided for this purpose in the pin 78 outboard the lugs oflatch 77.

Latch 77, as best seen in FIGS. 1 and 2, is substantially U-shaped withspaced apart parallel legs 77a, each having an aperture at one endthereof to receive the pin 78 and at its opposite end being connected bya cross web 77b to the other leg. The cross web 7712 is provided with aU-shaped notch 77c extending from a free edge thereof and positionedcentrally between the legs 77a. Latch 77 is pivotally supported on probeelectrode 42 so that the web portion thereof, when the latch ispivotedin a counterclockwisedirection with reference to FIG. 1, willextend slightly beyond the'collet chuck end of the probe electrode tohave the web 77b engage the underside of the head of a stud previouslyinserted in the collet chuck, the shank portion of the stud beingslidably received in the notch 770 of the web 77b. When the latch 77 ismoved to the position just described, the stud 16 will be retained andwill move with the probe electrodeupon axial movement of the probeelectrode.

To effect pivotal movement of latch 77, each of the legs 77a thereofintermediate the ends of these legs is provided with a hole to receive apin 81 to pivotally support between these legs the tube 82 fixed to oneend of a latch actuator pin 83, as seen in FIG. 3, extending through anaxially extending, elongated slot 84 in a web leg 47 of cylinder 43. Theopposite end of the latch actuator pin 83 has a push cap 85 affixedthereto whereby an operator depressing this push cap downward toward theweb leg 47 will cause the latch 77 to pivot in a counterclockwisedirection, with reference to FIG. I, about the axis of pin 78 intolatching engagement with a stud 16 positioned in the collet chuckportion of probe electrode 42.

Latch actuator pin 83 is normally biased in an upward direction relativeto the web leg 47 moving the push cap 85 away from this web leg, tonormally pivot latch 77, in a clockwise direction to the position shownin FIG. 1, by means of a coiled spring 86 encircling this actuator pinin position to abut at one end against the push cap and at its other endagainst a washer 87 encircling the actuator pin 83 and slidably engagingthe outer surfaceof the web leg 47 adjacent to slot 84.

In operating the subject in-ding repair tool 10, an operator would firstinsert the head of a stud 16 into the collet chuck end of probeelectrode 42 and then position the tool so that this stud is positionedin approximately the center of the in-ding 15a in panel 15. The operatorcould then push the weld gun 11 toward the panel 15 with sufficientforce so that the actuator rod 32 would move to close the contact oflimit switch SW-2 after which the operator could trigger the button 31of switch SW-l to effect firing the gun to thereby weld the stud 16 tothe panel 15.

However, in view of the switch arrangement in the preferred embodimentof the invention, the preferred mode of operation would be to have theoperator depress and hold the trigger button 31 of switch SW-l to closethe contacts of this switch and to then have the operator push the studwelding gun 11 toward panel 15 until the actuator rod 32 moves axiallyin the barrel of the gun a sufficient distance to close limit switchSW-2 to effect firing of the gun and therefore welding of the stud 16 tothe panel 15. This mode of operation is preferred since limit switchSW-2 is physically acted upon by actuator rod 32, which is an extensionof shaft 25 of the electrode spindle assembly 26 and, since the distanceof the shaft 25 travel in the barrel of the weld gun housing before theactuator rod will trigger the limit switch SW-2 is related to the springforce of spring 28, weld quality will be held uniform because the springpressure that controls the bias force of stud 16 against panel 15 willalways be the same when the gun is fired.

After welding of the stud 16 to the panel 15, and while still pressingthe welding gun 11 toward this panel, th operator would release thetrigger button 31 to permit opening of the contacts of switch SW-l andthen depress the cap 85 of the stud latch mechanism to pivot the latch77 into latching engagement with the stud l6 beneath the head thereof toaxially retain it for movement with the electrode spindle assembly 26.After welding of the stud 16 to the panel 15, the seat portion 48 withthe O-ring 50 thereon of the cylinder 43 would be resting on the panel15.

The operator, while still holding cap 85 depressed, would then depressthe push button 61 of the control valve 62 to place the conduit 64 influid communication with the cavity in front of the piston 54 in bore 45of cylindrical portion 44 of cylinder 43 so that fluid under pressurewill effect displacement of the piston and the electrode spindleassembly 26 to which it is attached in an axial direction relative tothe cylinder 43 which, as described, is in abutment against the panel 15whereby the in-ding 15a area of the panel is raised close to or slightlyabove the normal planar surface of panel 15. After this occurs, thoperator would release the push button 61 of the control valve 62whereby the piston cavity would be disconnected from fluid communicationwith the conduit 64 and placed in communication with the exhaust port63. The operator would then also release the stud latch mechanism topermit removal of the tool from the stud 16.

What is claimed is:

1. A hand-held and operated in-ding repair tool including an electricstud welding gun comprising a gun housing including a-pistol grip and abarrel having an axial stepped bore containing the operating componentsof said gun including an electrode spindle having one end thereofpositioned in said bore for limited forward and rearward axial movementtherein and having its other end which includes a weld stud retainingchuck at the free end thereof extending outward from the front of saidbarrel, resilient means positioned in said barrel to bias said electrodespindle in a forward axial direction, electrical weldng power meansextending through said pistol grip and being operatively connected atone end to said electrode spindle, said electrical welding power meansincluding an operator controlled switch mounted on said pistol grip ofsaid gun housing, a piston fixed to said electrode spindle intermediatethe ends thereof and exteriorly of said gun housing, cylinder meansincluding a cylinder slidaby encircling said other end of said electrodespindle and said piston to form with one side of said piston a variablevolume fluid chamber, means engaging the other side of said piston andengaging said cylinder to normally bias said cylinder means toward saidgun housing, conduit means connected at one end to said cylinder meansin fluid communication with said variable volume chamber, operatorcontrolled valve means mounted on said gun housing and connected to theother end of said conduit means and connectable to a source ofpressurized fluid, said valve means being operable for selectivelyconnecting said conduit means to a source of pressurized fluid and tothe atmosphere, said cylinder means including an annular panelengageable foo't member encircling said other end of said electrodespindle adjacent to said chuck and, manually operable latch meanspivotally connected to said electrode spindle for movement relative tosaid chuck between a stud retaining position and a stud releaseposition.

' 2. A in-ding repair tool according to claim 1 wherein said cylindermean includes an annular foot and axial extending, spaced apart web legsinterconnecting said cylinder with said foot with one of said web legshaving an axial extending elongated slot therethrough and wherein saidlatch means includes a U-shaped latch pivotally supported on saidelectrode spindle and having a stud engaging portion, a latch acutatorpivotally connected at one end to said latch and having its other endextending through said slot in said one web leg and, spring meansoperatively connected to said latch actuator to normally bias said latchto said stud release position.

3. A in-ding repair tool according to claim 1 wherein said electricalwelding power means includes a normally open second switch connected inseries with said operator controlled switch, said second switch beingpositioned in said barrel for actuation by said electrode spindle uponrearward movement thereof.

4. A hand-held, in-ding repair tool usable for welding a stud to anin-ding in a sheet metal panel and then pulling the in-ding out by meansof the previously welded stud, said in ding repair too] including a studwelding 8 gun including a gun housing having a pistol grip and a barrelwith said barrel having an axial stepped bore therein opening to thefront of said barrel an electrode spindle having a first shaft portionpositioned in said stepped bore of said barrel for limited reciprocalforward and rearward movement therein, resilient means positioned insaid barrel engaging said first shaft portion to normally bias saidfirst shaft portion in an axial direction forward toward the front ofsaid barrel, said electrode spindle further including a second shaftportion extending at one end from said first shaft portion outward fromthe front of said barrel and carrying at its opposite enda stud holderprobe electrode having a collet chuck at its free end adapted toreleasably support a weld stud, a piston fixed to said second shaftportion for axial movement therewith, a cylinder means including a fluidcylinder and a foot positioned axially outward from said cylinderadapted to encircle said collet chuck, said second shaft portion beingreciprocally joumalled in said cylinder means with said pistonpositioned in said cylinder for reciprocal movement therein, said pistonformingwith said cylinder on one side of said piston a variable volumechamber, spring means positioned in said cylinder on the other sideofsaid piston to normally bias said cylinder means in an axial directionwhereby said foot is moved in a direction toward said collet chuck,inlet port means in said cylinder in communication with said variablevolume chamber, conduit means including a valve, said conduit meansbeing connected at one end to said inlet port means and selectivelyconnected at its other end by said valve to a source of pressurizedaeriform fluid and to the atmosphere, manually operable pivotable latchmeans operatively connected to said stud holder probe electrode toreleasably secure a weld stud retained in said collet chuck for axialmovement with said electrode spindle assembly and, electrical weldingpower means, including an operator controlled switch on said pistolgrip, said electrical welding power means being electrically connectedto said first shaft portion to effect welding of a weld stud retained bysaid collet chuck.

5. An in-ding repair tool according to claim 4 wherein said cylindermeans includes axial extending, spaced apart web legs interconnectingsaid fluid cylinder with said foot with one of said web legs having anaxial extending elongated slot therethrough and wherein said pivotablelatch means includes a U- shaped latch pivotally supported on said studholder probe electrode, a latch acutator pivotally connected at one endto said latch and having its other end extending through said slot insaid one web leg and spring means operatively connected to said latchactuator to normally bias said latch to astud release position.

6. An in-ding repair tool according to claim 5 wherein said electricalwelding power means includes a normally open second switch connected inseries with said operator controlled switch, said second switch beingpositioned in said barrel for actuation by said first shaft portion uponrearward movement thereof.

1. A hand-held and operated in-ding repair tool including an electricstud welding gun comprising a gun housing including a pistol grip and abarrel having an axial stepped bore containing the operating componentsof said gun including an electrode spindle having one end thereofpositioned in said bore for limited forward and rearward axial movementtherein and having its other end which includes a weld stud retainingchuck at the free end thereof extending outward from the front of saidbarrel, resilient means positioned in said barrel to bias said electrodespindle in a forward axial direction, electrical weldng power meansextending through said pistol grip and being operatively connected atone end to said electrode spindle, said electrical welding power meansincluding an operator controlled switch mounted on said pistol grip ofsaid gun housing, a piston fixed to said electrode spindle intermediatethe ends thereof and exteriorly of said gun housing, cylinder meansincluding a cylinder slidaby encircling said other end of said electrodespindle and said piston to form with one side of said piston a variablevolume fluid chamber, means engaging the other side of said piston andengaging said cylinder to normally bias said cylinder means toward saidgun housing, conduit means connected at one end to said cylinder meansin fluid communication with said variable volume chamber, operatorcontrolled valve means mounted on said gun housing and connected to theother end of said conduit means and connectable to a source ofpressurized fluid, said valve means being operable for selectivelyconnecting said conduit means to a source of pressurized fluid and tothe atmosphere, said cylinder means including an annular panelengageable foot member encircling said other end of said electrodespindle adjacent to said chuck and, manually operable latch meanspivotally connected to said electrode spindle for movement relative tosaid chuck between a stud retaining position and a stud releaseposition.
 2. A in-ding repair tool according to claim 1 wherein saidcylinder mean includes an annular foot and axial extending, spaced apartweb legs interconnecting said cylinder with said foot with one of saidweb legs having an axial extending elongated slot therethrough andwherein said latch means includes a U-shaped latch pivotally supportedon said electrode spindle and having a stud engaging portion, a latchacutator pivotally connected at one end to said latch and having itsother end extending through said slot in said one web leg and, springmeans operatively connected to said latch actuator to normally bias saidlatch to said stud release position.
 3. A in-ding repair tool accordingto claim 1 wherein said electrical welding power means includes anormally open second switch connected in series with said operatorcontrolled switch, said second switch being positioned in said barrelfor actuation by said electrode spindle upon rearward movement thereof.4. A hand-held, in-ding repair tool usable for welding a stud to anin-ding in a sheet metal panel and then pulling the in-ding out by meansof the previously welded stud, said in-ding repair tool including a studwelding gun including a gun housing having a pistol grip and a barrelwith said barrel having an axial stepped bore therein opening to thefront of said barrel an electrode spindle having a first shaft portionpositioned in said stepped bore of said barrel for limited reciprocalforward and rearward movement therein, resilient means positioned insaid barrel engaging said first shaft portion to normally bias saidfirst shaft portion in an axial direction forward toward the front ofsaid barrel, said electrode spindle further including a second shaftportion extending at one end from said first shaft portion outward fromthe front of said barrel and carrying at its opposite end a stud holderprobe electrode having a collet chuck at its free end adapted toreleasably support a weld stud, a piston fixed to said second shaftportion for axial movement therewith, a cylinder means including a fluidcylinder and a foot positioned axially outward from said cylinderadapted to encircle said collet chuck, said second shaft portion beingreciprocally journalled in said cylinder means with said pistonpositioned in said cylinder for reciprocal movement therein, said pistonforming with said cylinder on one side of said piston a variable volumechamber, spring means positioned in said cylinder on the other sideofsaid piston to normally bias said cylinder means in an axial directionwhereby said foot is moved in a direction toward said collet chuck,inlet port means in said cylinder in communication with said variablevolume chamber, conduit means including a valve, said conduit meansbeing connected at one end to said inlet port means and selectivelyconnected at its other end by said valve to a source of pressurizedaeriform fluid and to the atmosphere, manually operable pivotable latchmeans operatively connected to said stud holder probe electrode toreleasably secure a weld stud retained in said collet chuck for axialmovement with said electrode spindle assembly and, electrical weldingpower means, including an operator controlled switch on said pistolgrip, said electrical welding power means being electrically connectedto said first shaft portion to effect welding of a weld stud retained bysaid collet chuck.
 5. An in-ding repair tool according to claim 4wherein said cylinder means includes axial extending, spaced apart weblegs interconnecting said fluid cylinder with said foot with one of saidweb legs having an axial extending elongated slot therethrough andwherein said pivotable latch means includes a U-shaped latch pivotallysupported on said stud holder probe electrode, a latch acutatorpivotally connected at one end to said latch and having its other endextending through said slot in said one web leg and spring meansoperatively connected to said latch aCtuator to normally bias said latchto a stud release position.
 6. An in-ding repair tool according to claim5 wherein said electrical welding power means includes a normally opensecond switch connected in series with said operator controlled switch,said second switch being positioned in said barrel for actuation by saidfirst shaft portion upon rearward movement thereof.